I really think that it wouldn't be as bad as you think. The takedowns are what are rough on the knees. Most jits schools will even let you start the rolling on your knees or from seated position, or from any other position like mount, side control, guard. Most lower belts also don't go for, and in tournaments are no allowed to use certain knee bars, heel hooks, or other things that could cause damage to the knee.

Plus, really, you can easily just be really picky about who you train with. Most jits schools aren't necessarily competition schools, or mma schools, so it's a little more laxed than you'd think.

Anyways, just a thought. I see many men and women who are older, are not athletes, and many have body issues or are overweight. In some cases, the rolling and stretching and going through techniques can stretch and strengthen the weak parts of our bodies. There's a lot of soft work, and you don't HAVE to roll to an extent where every roll is a 100% fight. Good communication is key, cuz some are there to train to fight.

But definitely not judging you if you think it's not for you or risky. Only you can assess where you are at and what can meet your goals safely, so I definitely support that! Definitely have to be smart when it comes to taking care of your body, and knees are important lol!